 It is common for a national health system to have a digital architecture composed of several information systems and applications that serve complementary functions. These systems may need to exchange information or talk to each other to reduce duplicate storage of data and help bring data from different sources together in a holistic way rather than keeping it in silos. This helps decision makers to obtain a broader, more detailed picture of what is happening in the health system as a whole and can also improve the operational efficiency of each individual system. The ability to send and receive information between different systems, software, and file formats is referred to as interoperability. For example, DHIS2 and OpenMRS, which stands for Open Medical Record System, are interoperable because they allow the sharing of data and data definitions with each other. In this example, a health system may use OpenMRS to store detailed medical records for each individual hospital admission among other hospital and patient data. Interoperability allows DHIS2 to receive relevant data from OpenMRS, such as aggregate data on total hospital visits, services delivered, and patient outcomes, or tracker data on individual patients, and use them for analysis in combination with other data stored in DHIS2. This is commonly referred to as a one-to-one integration, as you are linking one system directly to another. Interoperability depends on standards that can be broken down into two levels. First is content. This means ensuring that what is being shared between systems represents the same item conceptually. For example, that a hospital admission record in OpenMRS contains the same disaggregations for sex and age as the corresponding aggregate data element in DHIS2, or that the organization units in both systems are aligned. The second level is technical. This involves the mechanisms and formats used to actually transmit the data from one system to the other. In simple words, technical integration ensures that all systems involved can speak to and hear each other, and that they use the same language. One of the most common DHIS2 interoperability scenarios is using DHIS2 as a data warehouse. Let's look at an example. One country uses a software system that records and stores the results of laboratory tests used to detect tuberculosis cases. Another system manages the stock of medicines in the facilities and alerts supply chain managers when there is a stock shortage. A third system collects human resource data to help manage and allocate health center staffing. Data from these separate systems flow into DHIS2. In this scenario, the DHIS2 platform functions as an integrated data warehouse, hosting data from various sources and systems so that they can be utilized holistically to enable informed decision making. While this scenario involves more than two systems, it is still an example of one-to-one integration because each system is integrated with DHIS2 directly without those external systems being able to talk to each other. In other scenarios, instead of using DHIS2 to combine data from other systems, data in DHIS2 may be sent to other systems that require it. For example, DHIS2 may send national disease surveillance data to a regional surveillance information system to facilitate cross-border surveillance of infectious diseases. In some cases, this may mean exchanging data between two or more DHIS2 systems. There are also more complicated scenarios where DHIS2 is one of a network of several different systems sending and receiving data from each other. This is an example of end-to-end or many-to-many interoperability. This can be achieved through the use of an interoperability layer, which is a separate piece of software that coordinates the exchange of data between multiple systems. In each scenario described in this video, interoperability is not as straightforward as simply connecting the systems to each other. Interoperability is a process that requires strong governance to coordinate content across systems, including the initial work to align or map data between systems, as well as technical support for the initial integration, and an ongoing basis as systems are updated and modified, and as the larger information system architecture changes. In summary, interoperability refers to the ability to send and receive data between different systems, software, and file formats. Using DHIS2 as a data warehouse is one of the most common DHIS2 interoperability scenarios. This term refers to how DHIS2 can be used to receive data from multiple information systems and sources to facilitate data triangulation. DHIS2 data can also be sent to other platforms or systems that need it.